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X-CSE-ConnectionGUID: b0Baa+LySKijhdD6xCrbTA== X-CSE-MsgGUID: Xwk4PC4iQiiNGNWF+VLVCg== X-IronPort-AV: E=McAfee;i="6800,10657,11841"; a="107201099" X-IronPort-AV: E=Sophos;i="6.25,154,1779174000"; d="scan'208";a="107201099" Received: from fmviesa003.fm.intel.com ([10.60.135.143]) by orvoesa101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Jul 2026 09:48:24 -0700 X-CSE-ConnectionGUID: TPekdXm6QFeyR2snD9ujBA== X-CSE-MsgGUID: LUfFnIGrQbuyaq23s9B0lA== X-ExtLoop1: 1 Received: from sghuge-mobl2.amr.corp.intel.com (HELO [10.125.111.199]) ([10.125.111.199]) by fmviesa003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Jul 2026 09:48:23 -0700 Message-ID: Date: Fri, 10 Jul 2026 09:48:22 -0700 Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] x86/virt/tdx: Formalize SEAMCALL version encoding support To: Kiryl Shutsemau Cc: Xu Yilun , x86@kernel.org, linux-kernel@vger.kernel.org, rick.p.edgecombe@intel.com, dave.hansen@linux.intel.com, yilun.xu@intel.com, chao.gao@intel.com, djbw@kernel.org, linux-coco@lists.linux.dev, peter.fang@intel.com, xiaoyao.li@intel.com References: <20260708170330.83850-1-yilun.xu@linux.intel.com> Content-Language: en-US From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/10/26 09:21, Kiryl Shutsemau wrote: > The version is not a register operand, it is part of the function > number. I'm not sure why that's important. Sure, the arg structure is all full registers now. But it's not even all the registers because RAX isn't there. So let's say we made the data structure smarter: struct tdx_module_args { union { u64 rax; struct { u16 function_nr; u8 version u8 padding0; u32 flags; }; }; u64 rcx; u64 rdx; ... } All of the: struct tdx_module_args args = {}; instances would default to version=0. It would take a one-liner to get bit 63 set: static int seamldr_call(u64 fn, struct tdx_module_args *args) { ... + args->flags |= SEAMLDR_BIT; guard(raw_spinlock)(&seamldr_lock); return seamcall_prerr(fn, args); } The truth of the matter is that 'fn' *IS* the RAX from the TDX ABI. We're carrying it around the kernel in that format, and it just doesn't work very well. The alternative is to carry the logical pieces of RAX around the kernel and them assemble RAX out of them in one (or very few) places. *Not* to build RAX in the TDX module ABI early far from the TDX module ABI layer itself.